NOUMENON (Gr. voouµevov, a thing known, from voeiv)  , a philosophical term put into currency by Kant and not much used except in definite reference to his doctrine . In the Kantian system the term " noumena " means things-in-themselves as opposed to " phenomena " or things as they appear to us . According to Kant the human mind is such that it can never penetrate by its speculative powers to things-in-themselves, but can only know phenomena . Thus we have the odd position that noumena, or the contents of the intelligible world, are just the things to which thought can never penetrate . The term, however, is a relic of an early period of Kant's mental development . In his fully mature or critical position he held that the noumenal world was inaccessible to the speculative reason, and yet that we are not altogether excluded from it, since the practical reason, i.e. our capacity for acting as moral agents, assures us of the existence of a noumenal world wherein freedom, God and immortality have a real place . The relation of noumena to phenomena in the Kantian system is a most difficult one; and, in view of the fact that the acutest intellects of Europe have been engaged vainly for more than a century in reconciling the various passages on the subject, the safest conclusion is that they are irreconcilable . The course adopted by Kant's immediate successors in German idealism was to reject the whole conception of noumena, for the reason that what is essentially unknowable has no existence for our intelligence . Kant, however, protested strongly against this development when it was propounded by Fichte, and held that he had precluded it by his " refutation of idealism": he stood unshakably to the belief in an absolutely real world behind phenomena . Kant's position may be illogical as he himself stated it; but it is the expression of a sound principle: we must connect it with his general tendency to recognize the dynamic side of things . He saw, what so many of his successors failed to see, that the world as we know it is an expression of power; and he could not imagine whence the power could come if not from a world beyond phenomena . (See KANT; PHENOMENON.) (H .